| They sell a tapered-end seat extractor tool and you drive it in with sharp quick blows with a hammer and it will cut new ridges and allow you to unscrew the seat.
Whenever you work on plumbing jobs you must think things through in advance so as to not cause yourself grief. It is for reasons like what you gave as to why many people don't like working on plumbing. It can be sort of surgical at times. I have always been able to get out a seat under similar stripped circumstances. The key is patience. Do NOT try to turn the tool until you are pretty sure you have cut grooves into the sides of the brass seat and can get a good bite on it. For added power slip a cheater pipe over the handle and go slow. With any luck, like the good luck I have, it will go "snap" and crack loose and come out. |